Circuit breaker plug



April 28, 1936; A, TAESSER 2,038,970

CIRCUIT BREAKER PLUG Filed NOV. 19, 1935 tion Patented Apr. 28, 1936 UNITED STATES PATENT OFFICE 1 Claim.

tral terminal of the plug with a coiled thermostatic spring having a terminal at its end which is normally engaged with a terminal on the plug base, the arrangement being such that the spring will tend to straighten when it is heated by an overload, breaking the circuit, and will return to normal position when its temperature returns to normal, restoring the circuit, the construction permitting the tension with which the terminals are held in contact to be varied.

For a more complete disclosure of the invention reference is made to the following specification, in connection with the accompanying drawing, in which:

Fig. 1 is a central longitudinal sectional view oi. circuit breaking plug embodying my inven- Fig. 2 is a side view thereof partly broken away.

Fig. 3 is a cross section, at line 3-3 oi. Fig. 1.

Fig. 4 is a detail view of the thermostatic device which is employed, on a greatly enlarged scale, and

Fig. 5 is a detail view oi. the member with which it contacts.

As shown in the drawing, the plug comprises a cup shaped base or top member a. of insulating material and a bottom member b, also of insulating material, said member b having an annular flange'c at the end which seats on the top member and having a terminal (1 in the middle thereof which extends from its bottom to its top end. A metal sleeve e is formed to provide an internal screw thread which is adapted to be received by a corresponding external screw thread on the top member a and said sleeve has an inturned flange ,f at its outer end which is arranged to engage the flange c, so as to clamp the top and bottom members together.

According to my invention the terminal (1 is extended beyond the inner side of member I and a spirally formed thermostatic arm ,1 of resilient conducting material is connected at one end to said terminal :1 and extends about the same and has a terminal h at its opposite end, said arm being formed from two resilient strips having different ooefllcients of expansion, as indicated in Fig. 4, and said terminal h being preferably formed of some hard metal, as steel. A U- shaped contact device or clip i, shown in detail in Fig. 5, is arranged on the rim portion oi. the cup shaped top member a, so that the outer portion is in contact with the sleeve e and its inner portion extends within the cup of member a and has a terminal 7c arranged in position for engagement with the terminal 72..

When the parts are assembled the sleeve e is screwed onto member a, and before it is screwed tight, the member b is turned until terminal h is engaged with the terminal k on the inner leg of the clip 1', the member b being turned until the spring arm g is placed under suihcient' ten- .sion to insure a strong contact, and then the sleeve is screwed tight, holding the member b securely in this position on the member a. As thus arranged, the terminal d will be electrically connected in the sleeve 6.

When an overload comes on to the circuit, the spring arm 9 will be heated and the unequal expansion of the metals of which it is composed will cause the free end portion of the arm to straighten slightly, thereby causing the terminal h to be moved out of contact with the terminal 10, as indicated by the dotted line position of Fig. 3, so that the circuit will be broken. As soon as the circuit is broken, the arm will return to normal temperature and move the terminal it back into contact with the terminal k, restoring the circuit.

-With the above described construction the circult will be almost instantly broken when overloaded, and will be immediately restored, and if the overloaded condition has not been removed it will be broken again.

I claim:

A circuit breaker plug comprising top and bottom members of non-conducting material, an exteriorly disposed sleeve of conducting material for connecting said members having a threaded connection with said top member, and a flange engaged with said bottom member permitting relative rotatable adjustment thereof, said bottom member having a centrally disposed terminal extending internally thereof, a resilient thermostatic arm connected at one end to the inner end of said terminal and extending spirally therefrom transversely of the plug, and a terminal mounted on said top member, electrically connected with said sleeve and having an inner portion thereof arranged for yieldable engagement by the opposite end of said arm according to the relative adjustment of said members.

LOUIS A. TESSIER. 

